Snooping Protocals

Snooping, in a security situation, is illegal access to another person's or company's data. Snooping can consist of informal observance of an e-mail that appears on another's computer screen or watching what someone else is typing. More complicated snooping uses software programs to distantly monitor bustle on a computer or network device. Snooping techniques, to monitor keystrokes, detain passwords and login information, and to catch e-mail and other private communications and data transmissions. Corporations sometimes snoop on workers legally to monitor their use of business computers and track Internet usage; governments may watch on persons to collect information and avert crime and terrorism. In a snooping system, all caches on the bus monitor the bus to determine if they have a copy of the block of data that is requested on the bus. Every cache has a copy of the sharing status of every block of physical memory it has. Multiple copies of a document in a multiprocessing environment typically can be read without any coherence problems; however, a processor must have exclusive access to the bus in order to write.
There are two types of snooping protocol
1.Write invalidate
Read-broadcast is not suitable for sequential sharing
It may prove beneficial in the single-producer, multiple-consumer situation
2.Write Update
Competitive Snooping is advantageous if there is sequential sharing